The basic constituents of any solar energy collector include a collector element, glazing, and an enclosure frame (preferably insulated), to support the glazing and the collector element. The ability of a solar collector to collect solar energy is a function of the collector element surface area and the orientation of the collector surfaces relative to the incident angles of the sun. The ability of a solar collector to transfer the collected energy to the desired media (air, liquid, etc.) is a function of the collector element surface area and the distance the media travels over the collector element. Heat losses are a function of the type and number of glazing utilized and the insulation capacity of the frame enclosure. Cost effectiveness of the collector is a function of the effective use of low cost materials and designs which lend themselves to automated mass production. Numerous solar collector designs have evolved over the years. However, none of these designs have attempted to optimize all of the above mentioned parameters in a single solar energy collector concept.
Accordingly, it is an object of this invention to optimize all of the above mentioned parameters in a single solar energy collector. The concept of a structural core as in U.S. Pat. No. 3,645,833 (filed May 20, 1970 and issued Feb. 29, 1972) gave direction of the structural core of U.S. application Ser. No. 45,918 (filed Aug. 17, 1979) which in turn, evolved into the invention of the instant application.
The instant invention comprises a solar energy collector employing a unique collector panel which, besides serving as an efficient solar collector, also serves as: the basic structural member of the collector providing inherent structural integrity; the frame for single or multiple glazing; a portion of the integral ductwork for the transfer media.
The energy collector panel comprises a plurality of collector pockets in the form of concave, tapered, truncated, three dimensional polyhedra. These pockets of three dimensional polyhedra provide numerous exposed surfaces which are oriented at various angles relative to the path and azimuth of the sun as it sweeps its arc across the sky. Thus, there are always some surfaces favorably inclined relative to the rays of the sun. The relative positioning of the pockets is such that, as one internal surface of a polyhedra begins to become shaded, a neighboring surface begins to receive sunlight. Due to this structure, positioning of the collector relative to the sun is not critical. It is also contemplated that each pocket may be in the form of a cone or truncated cone.
The solar energy collector panel can be made from any of the moldable materials including, but not limited to, plastics, metals, wood products, and composites. The pockets of the panel may be identical in size and shape or may be any combination of various sizes and shapes of polyhedra. By incorporating regularly or irregularly placed polyhedral pockets of various sizes and/or shapes into the collector, different degrees of curvature may be accomplished. This curvature may range from flat to compound to spherical, and the geometry necessary to produce the desired curvature can be determined analytically. This collector structure provides increased compressive strengths and increased flexure stiffness.
Structural efficiency is derived from joining the bases of the polyhedral pockets of greatest depth to a (preferably insulated) back cover to produce a sandwich structure in which the pocketed collector panel serves as an integral core, as well as a partial face sheet. By design, the collector panel also serves as the collector closure (sides, top, bottom) and as a frame for the glazing. The sides and top of the collector panel also are designed to present themselves to the sun's rays, thus acting as an uninsulated, unglazed collector member. The sides, top, and glazing framework are an integral part of the collector panel and can be fabricated in a single operation, thus lending to low cost, automated, mass production.
Additionally, the design and placement of the core polyhedra is such that they provide, in combination with the back member, a natural path (ductwork) for the transfer medium (air). Thus, little or no additional ductwork is required. The design of the collector is such that the flow path of the media starts at the top of the collector (between the unexposed surface of the collector and the back cover) and proceeds to and through holes in the bottom of the collector element. The medium then flows upward between the glazing and the front exposed face of the collector. Since the medium flows over both the unexposed surface and exposed surface of the pocketed collector panel, the effective heat transfer area is greater than that of a flat panel. As such, the design provides excellent heat transfer to the medium and minimizes the need for insulation.
Venting of the heated medium to the room or area to be heated is accomplished by a simple external vent housing which must include inlet and outlet ports (with or without directable louvers) attached to holes in the back cover of the collector and a circulation device (such as a fan or pump). Any material or design can be used for the vent so long as it is compatable with the inlet/outlet ports in the collector.
Since the collector panel and attached back cover provides a high degree of structural efficiency, the collector is self supporting and may be used as a mounting unit for through-window, through-wall, and the like installation.
In one preferred embodiment of the invention, each solar energy collector pocket is a minor variation of a tetrahedron, more preferably a truncated tetrahedron. It is a documented fact that a tetrahedron has the highest surface area to volume ratio of any known regular three dimensional shape. The pocketed collector panel increases the surface area presented to the sun by a factor of at least 2.5 over a flat plate panel, thus providing a highly efficient, exposed shape for solar energy collection.